Heartfield said: "I am leaving the best job, an amazing agency and some of the most talented people I have ever worked with. That should hopefully give an indication of the uniqueness of the opportunity James and David approached me with and the scale of our ambition to make something great together."

There has been much speculation about who Murphy and Golding would choose as their creative partner; the pair have been open about their desire to find a "weapons-grade" creative. Several of the most respected creatives in London – male and female – are understood to have had conversations with the duo about the role.

Heartfield is one of the most decorated creatives in the UK. His awards haul includes Grand Prix at Cannes Lions and The One Show, and he was named most awarded copywriter in the world in 2006.

He joined BBH in 2010 as creative director and became the agency’s chief creative officer in 2018. During his time there, he has overseen award-winning work for clients including Barclays, Kronenbourg 1664 and Audi, which won the IPA Effectiveness Grand Prix last year. Before BBH, Heartfield worked at Ogilvy, Abbott Mead Vickers BBDO and Fallon.

Murphy and Golding, who left Adam & Eve/DDB in the spring, said: "We’re beyond excited that Ian will be the creative founder helping us to build a new exciting team."

The as-yet-unnamed agency is due to launch in the first half of 2020, once Murphy and Golding’s 12-month non-compete restriction expires.

Neil Munn, global chief executive of BBH, said: "Ian has accomplished a huge amount as a creative leader of BBH. We are sorry to see him go after nine years, but are blessed to still have an extraordinary amount of senior talent who will no doubt continue to carry the torch for creative excellence."